I always thought almost everyone should eat about 2,000 calories a day, because that's what is listed on Nutrition Facts labels. But my doctor told me almost no one should eat 2,000 calories a day. Can you clarify this?

The number of calories you should consume each day is personalized, as much as it can be, according to your age, your sex and your activity level.

Calorie recommendations for adults range from a low of 1,600 calories a day for sedentary women 51 or older, to a high of 3,000 calories a day for active men from 19 to 35.

Even though the standard of 2,000 calories a day is appropriate for only a few groups -- including sedentary men who are 61 or older and moderately active women between 31 and 50 -- it's not a bad standard to base Nutrition Facts information on. That number (2,000 calories) really only affects the percentages listed under the label's "Daily Values" for fats, carbohydrates and fiber. Since the actual content (in grams) of those food components is also listed, it's relatively easy for a person who uses the label to make decisions about their diet to make adjustments accordingly.

For example, if you're a moderately active 40-year-old man who is in a healthy weight range, your calorie intake should be about 2,600 calories a day. Since fat, carbohydrate and fiber intake are based on that higher calorie level, you know you can aim for more than 100 percent of the Daily Value of those items over the course of the day -- 130 percent, in fact, since 2,600 calories is 130 percent of 2,000 calories.

All that detail aside, the bigger point is that everyone should know about how many calories they should be eating each day. To find your level, see the chart from the 2010 Dietary Guidelines for Americans, posted online at http://bit.ly/calneeds.

To determine how active you are -- a key element in figuring out your calorie level -- use these guidelines:

• "Active" means you engage in physical activity equivalent to walking more than 3 miles a day at a rate of 3 to 4 miles per hour.
• "Moderately active" means your physical activity averages the equivalent of walking 1.5 to 3 miles a day at the same pace.
• "Sedentary" means you generally don't engage in daily physical activity beyond that associated with day-to-day life.

For more about physical activity, see this Health and Human Services fact sheet: http://bit.ly/physactivity.